The present invention relates generally to compression dead-end and compression joint connector assemblies. More particularly, the present invention discloses a compression connection assembly for use in both dead-end and mid-joint conductors, such as are further typically employed in transmission line installations, as well as a method for constructing such a connection assembly.
Connector assemblies are generally known in the art and such as is are particularly used with high current transfer (power) cables utilized in conventional transmission line applications. Such conductor lines typically incorporate outer layers of such as high temperature aluminum strands, as well as inner layers or xe2x80x9ccorexe2x80x9d of such as aluminum matrix composite wires. It is also known that this conductor core exhibits fairly significant longitudinal strength, on the order of 240 kips per square inch (ksi) while that the same time having limited (typically on the order of 20 ksi) transverse strength properties.
In application, it is desirable to communicate the extending end of a given length of power cable, in both an insulated and effective current conducting fashion and such as to a succeeding and interconnecting length of cable. Alternatively, another conventionally known connection for such a current transfer line is to an insulator string associated with an overhead tower or transmission support structure and such as is conventionally known as a xe2x80x9cdead-endxe2x80x9d connection.
In establishing either of the above types of connections, it is further desirable in the art to compress an encircling tube or barrel, typically constructed of steel, and associated with the connector assembly. A composite core of the current transfer line is inserted into one end of the steel barrel, the barrel subsequently being subjected to an area reduction/compression operation (operating at pressures of 10,000 psi or more) and upon inserting the barrel between a pair of heavy duty compression dies. The objective of this operation is to fixedly secure the current conductive core within the steel jacket and in the desired current carrying manner with respect to the succeeding cable or dead-end connector.
A specific problem uncovered in the compression of the steel barrel is the tendency of the core to damage or fracture as a result of it subsequent tensioning after installation and in use. It has also been determined to be desirable to establish a tensioning grip to the core in use up to 95% of its rated strength. The core must further be maintained in a substantially linear extending fashion during the initial mechanical die compression, else the subsequently applied tension will focus only on a portion of its strands, resulting in damage by crushing, notching or bending of the core.
It has also been determined that, as the composite core exhibits fairly low ductility elongation properties, it is required that the outer strands of the current carrying cable be loaded prior to those of the core, or else premature failure of the core will occur. An additional requirement of the connector is that it must be designed to retain the outer strands of the cable without damage and again in order to achieve a 95% desired rated strength of the cable.
An example of a prior art cable connector includes U.S. Pat. No. 3,384,704, issued to Vockroth, and which teaches a high tensile electrical connector for joining stranded cables. Vockroth includes an outer ferrule with a pair of tapered gripping jaws disposed in spaced relationship to the ends of the ferrule. The jaws grip the core strands of the cables to establish the desired mechanical connection, and the ferrule is subsequently gripped at both ends onto the connector strands of the cable to establish the electrical connection. During crimping, the conductor strands and the ferrule extrude longitudinally and pull the core strands and jaw into tighter engagement.
A further example of a wedge dead end to support aerial cables is disclosed in U.S Pat. No. 5,647,046, issued to Cowen, and which includes an assembled frame with an attaching cable for mounting to the support structure and two wedges that slide into the frame. The frame further consists of two parallel plates, each plate including two tapered and opposingly angled slots. The wedges are similarly tapered enabling them to be locked with the side plates and both also include a groove sized and textured to grip a specified cable. The wedges can be designed to compress the encased cable evenly along the entire contact surface of the wedge or with varying force along such surface.
The present invention discloses a compression connection assembly for use in both dead-end and mid-joint conductors, such as are further typically employed in transmission line installations. Also disclosed is a method for constructing such a connection assembly.
The connection assembly includes the provision of an aluminum sleeve insert in disposed fashion between the outer steel tube and the inserted composite core, the aluminum insert providing the combined characteristics of increased ductility and rate of extrusion (versus the steel sleeve) and in order to prevent force misalignments to the core (during the compression of the steel tube) which will result in subsequent failure of the connector assembly when it is placed under tension. This is in large measure due to the ductile characterstics of the aluminum insert which, during forced die compression of the outer steel tube, redistributes in interstitial filling manner within the spaces created between the core wires, as well as extruding beyond the annular disposed end of the steel tube and in order to achieve desired stress relieving between the interiorly held core and compression length.
A current carrying cable, such as is known in the art, includes a plurality of outer strands and a central extending plurality of inner strands and which are inserted within the aluminum sleeve prior to the compression forming operation of the steel tube. An outer tubular body is preferably constructed of a conductive and current carrying material such as aluminum and is slidably engaged over the assembled tube and sleeve upon the same being fixed to the central plurality of cable strands.
The outer tubular body is configured in either a dead-end application, and which includes a forged and extending eyelet for connecting an extending end of one cable to such as an aerial tower or pole. Alternatively, the outer tubular body is configured in a joint application for interconnecting opposingly extending ends of first and second cables, such as in mid-span between spaced apart towers or poles.